In certain applications, for example in the field of amateur astronomy, it is of interest to accurately determine the instant of occurrence of an observable phenomenon based on a reference time, for example in order to then correlate the images taken from different geographical positions and obtain accurate information on this phenomenon.
In this scenario, the optical instrument for example corresponds to a camera or a photometer intended to shoot images of an eclipse of one star by another celestial body.
For dating the images, it is notably known how to provide the device with an electronic case connected to the output of the optical instrument and able to superpose onto the data transmitted by the optical instrument, a date representative of the reference time provided by the receiver.
This is for example described in document IOTA Observer's Manual published on the site of the IOTA association, which is the acronym for “International Occultation Timing Association”. In this document, the reference clock signal is the GPS time signal which is a universal reference time.
The reference time receiver then transmits to the electronic case, a signal with one pulse per second in reference time, also known under the name of 1PPS signal, each pulse giving rise to synchronization of the internal clock of the electronic device with the reference time.
The date indicated by the internal clock of the case is then added as an overlay on the data from the optical instrument.
The case then delivers at the output a video flow which may be viewed on a screen and corresponding to the images from the optical instrument on which the date of the internal clock of the electronic case is displayed as an overlay.
However, this device has a certain number of drawbacks.
First of all, insofar that the electronic case is connected to the output of the optical instrument, the electronic case and the optical instrument must be compatible. Thus, the latter must have a compatible interface, and the electronic case should be able to read the format of the video data delivered by the optical instrument.
Further, the video flow delivered by the electronic case itself has a given format, which again induces compatibility problems of the video flow delivered with recording or read-out apparatuses.
Finally, the time-stamping of images imposes availability of viewing and recording means for the video flow leaving the electronic case, and therefore availability of a cumbersome piece of equipment incompatible with the conditions under which the sensing of images is generally achieved.